1. Field of the Invention
The present invention relates to high frequency switches typically used in the RF circuits of mobile phones.
2. Background Art
A known structure of a high frequency switch used in an RF circuit of high frequency wireless apparatuses such as mobile phones is to mount a PIN diode on a multilayer board with a built-in strip line. (For example, refer to Japanese Laid-open Patent No. H8-97743 (pp. 3-4, FIGS. 1, 2, and 3).)
Ever greater integration of the high frequency switch and other high frequency components such as high frequency filters and amplifiers disposed around the high frequency switch is being seen. To allow integration, high frequency switches mounted on the multilayer board need to be downsized to secure extra space for mounting other high frequency components. One currently proposed method for downsizing high frequency switches using a PIN diode is the use of a field-effect transistor switch (FET switch) as a high frequency switch. (For example, refer to Japanese Laid-open Patent No. H9-181588 (p. 4, FIG. 1).)
However, if FET switches are employed, each FET switch needs to contain multi-step FETs, such as four- to eight-step FETs, taking into account the withstand voltage of FETs configuring the FET switch for high frequency signals input from a transmission port. This hinders sufficient downsizing of the high frequency switch and blocks integration.